A known seat sliding apparatus, as disclosed in JP2002-154356A, includes a lower rail fixed to an upper surface of a vehicle floor, an upper rail fixed to a lower surface of a seat of the vehicle and mounted on the lower rail for forward and backward movement, a lock mechanism having a lock lever for releasably locking the upper rail to the lower rail, and slide supporting members (ball units) disposed between the upper rail and the lower rail to support both of the rails in a way that the upper rail slides along the lower rail.
As illustrated in FIG. 4 of JP2002-154356A, a lock portion is formed at a longitudinally center portion at one side portion of the upper rail, a lock portion into which the lock lever is fitted in an engaged and disengaged manner. The sliding portions are provided at both sides of the longitudinally center portion of the upper rail in a way that the slide supporting members come in contact with the sliding portions.
In other words, the sliding portions and the lock portion are arranged at the upper rail in series along the longitudinal direction.
In the seat sliding apparatus described above, it is necessary that an entire length of the upper rail and the lower rail needs to be longer by a length of the lock portion than a sliding length of the upper rail on the lower rail because the sliding portions and the lock portion are arranged at the upper rail in series along the longitudinal direction. Furthermore, as it is clearly illustrated in FIG. 5 and FIG. 6 of JP2002-154356A, the cross sectional shape of the upper rail is changed at the boundary between the sliding portions and the lock portion, resulting in difficulty in production.
The present invention has been made in view of the above circumstances, and provides a seat sliding apparatus for a vehicle, which is produced easily and achieves high mechanical strength even shortening the length of the upper rail and the lower rail.